In general, in metal parts such as vacuum joints, vacuum seal valves, liquid or gas pipe joints and seal valves which are made with a high carbon stainless steel as a base material, in order to form the respective constituent members into one body, normally, seal materials such as copper, gold, aluminum, fluorinated resins, rubbers and polyimide are used.
However, in the metal parts which use such seal materials, there are problems in that not only the number of parts increases but also assembly and manufacture steps thereof become complicated. Furthermore, when the metal seal material such as copper is used, since the seal effect depends on the softness of copper per se, the metal fatigue is caused owing to damage and abrasion applied on copper per se, as a result, the seal effect is remarkably deteriorated and the longer lifetime of the metal part itself cannot be obtained, still furthermore, a fluorinated resin seal material is poor in sealing power against helium gas, and the rubber and polyimide seal materials are poor in heat resistance.
In addition, wastes of the seal materials after the use become industrial waste. Accordingly, there are many problems, for example, countermeasures against environmental contamination are required.
Accordingly, development of a stainless material that renders the seal materials unnecessary from stainless metal parts such as vacuum joints, vacuum seal valves, liquid or gas pipe joints and seal valves that are mentioned above, can realize all-stainless seal/joint system products which are excellent in durability, is excellent in resilience and abrasion resistance and tender to environment is in strong demand.